6th Dec 2011 ISOLDE Workshop, CERN

Reaction Dynamics studies with 6,7Li and 9Be nuclei at Pelletron, Mumbai, India

Vivek ParkarUniversity of Huelva, Spain

Previous affiliation :Bhabha Atomic Research Centre, Mumbai, India

Outline of Talk:

Introduction to 14UD Pelletron facility, Mumbai, India

Studies with stable weakly bound (6,7Li and 9Be) nuclei:

Fusion cross-sections

Inclusive and exclusive breakup

Dipole Polarizabilities of 7Li and 9Be

Future prospects with light RIBs at ISOLDE

Started in 1988

A] Basic Research

Reaction studies near barrier

Fission studies

Nuclear Structure

Atomic Physics

Radio Chemistry studies

Magnetism

B] Applied Research

Radiation damage studies

Radiation Biology

Accelerator Mass

Spectroscopy (AMS)

Track etched membrane

Bio-environmental studies

http://www.tifr.res.in/~pell

Reactions with stable weakly bound nuclei

Low breakup threshold

Stable ions

6Li +d, Sd=1.48 MeV

7Li +t, St=2.47 MeV9Be ++n, Sn=1.57 MeV

Advantagelarge intensity and good beam quality

Study effect of breakup channel on elastic scattering and fusion cross-sections

Inclusive and exclusive breakup studies

Next step: Reaction dynamics with light RIBs

Fusion cross-sections from online and offline ray measurements

6,7Li+144,152Sm6,7Li+90Zr6,7Li+198Pt6,7Li+165Ho6,7Li+159Tb9Be+124Sn9Be+89Y

Motivation :Fusion in presence of breakup channel enhance fusion due to coupling OR suppress fusion due to loss of flux

Online ray technique: When ER is short lived (few secs) ray de-excitation from the excited states of that ER

Offline ray technique: When ER is long lived (few mnts - days) Measurement of rays after beta decay/Electron capture

Fusion = Σ ER

Evaporation Residue Measurement

Off-beam intensities of charac-teristic -lines from decay ofER and half-life were measured

F.C.Target &Catcher

Beam

P. K. Rath et al., PRC 79, 051601R (2009) (Rapid Communication)

Suppression (~28%) at E>Vb breakupEnhancement at E<Vb target deformationEffect of breakup and deformation coexist

Projectile breakup vs. target deformation

P. K. Rath et al., Nucl Phys. A (Accepted)

V.V.Parkar et al., PRC 82, 054601(2010)C. Palshetkar et al.,PRC 82, 044608 (2010)

Systematic of fusion suppression factor

(i) For a particular projectile, the suppression factor is more or less independent of the product ZPZT , (ii) suppression increases with decreasing breakup threshold of the projectile.

Exploring fusion at deep sub-barrier energies

New sensitive off-beam method KX - rays coincidence A. Lemasson et al., NIMA 598, 445 (2009)

A. Shrivastava et al., PRL 103, 232702 (2009)

Inclusive and Exclusive breakup study

6Li+65Cu6Li+209Bi6,7Li+90Zr9Be+89Y

Measurements: typical 2D

spectra

E (arb. unit)

E (

arb

. un

it)

7Li

6Li

t,d,p

(a) (b)

(c) (d)

Beam:6Li, Pelltron @TIFR

Energy: 24-50 MeV

Target:209Bi ~330 g/cm2 self-supporting

4 telescopes of SSB

Inclusive alpha production

No evaporation alpha; E

evp<Ecent

incl ~ direct reaction

Universal behaviour of inclusive alpha cross-sections

S. Santra et al., Phys. Rev. C (Submitted)

Below barrier, = Reaction

Otherwise, CF+Reaction

Complete reaction picture for 6Li+209Bi

Exclusive breakup study of 6Li

FC

209Bi(1 mg/cm2)

6Li Beam(~40nA)

250

100

100100 T1

T2(d)

T3()

T4(d)

M1

M2

Detectors: 2 telescopes (E: ~ 33 and E: ~ 500), 2 telescopes (E:~150 and E: ~1000), and 2 single monitors (E ~ 2000) of Si surface barrier detectors

Measured: Light charged particles in singles as well as coincidence, in list mode

Angular range: 50o-170o.

Energy: 36 and 40 MeV

Projectile breakupDirect breakup: Projectile breaks up directly into fragments at any

excitation energy larger than breakup threshold.

Sequential breakup: Projectile excited to resonant state followed by breakup, or it can exchange a few nucleon with the target and then breaks up.

6Li209Bi

d

6Li6Li

6Li

6Li* 6Li*5Li

209Bi209Bi

d p

n

Typical two dimensional spectra with and

without coincidence conditions.

E(MeV)

15 20 25 30 35

Cou

nts

0

10

20

30

[a]

[e]

[f]

td

p

d

6Li

7Li

E (MeV)E (MeV)

E

(M

eV)

E

(M

eV)

E

(M

eV)

E

(M

eV)

[c]

[d]

[b]

Cou

nts

Ch. No.

T1 @ 55o T2 @ 65o

Inclusive and exclusive -production

CDCC results with full coupling agrees with the average of two sets of experimental data for 3+ resonant state

Total d (theory) << (incl)

p(exp) + d(th) << (incl)

Other possible sources : (1) (6Li,4He) (2) (6Li,5Hen+4He) (3) (6Li,7Li4He+t)(4) partial fusion (d-cap)

Breakup of 6Li at 40 MeV

d/d (m

b/sr

)

10-2

10-1

100

101

102

-d-sequential (expt.)-d-direct (expt.)-p-total (expt.)-d-sequential (theory)-d-total (theory)-inclusive (expt.)

Breakup of 6Li at 36 MeV

c.m. (deg)40 60 80 100 120 140

d/d (m

b/sr

)

10-2

10-1

100

101

102

[a]

[b]

S. Santra et al., PLB 677, 139 (2009)

Dipole polarizability of 7Li, 9Be

Elastic scattering

Centre of matter distributions and centre of charge distributions of a nucleus do not coincide (e.g. deuteron, 7Li, 6He, 11Li etc.) in the presence of strong

electric field. Transition between states of opposite parity. (For normal nuclei states of opposite parity are at high excitation energy)For weakly bound nuclei low breakup threshold,

continuum states of opposite parity are nearby. The effect is very small. (2% change in elastic cross section of d + 208Pb (αd=0.70 fm3), Similar effect

expected for 7Li + 208Pb (α7Li =0.018-0.048 fm3).

Introduction

Beam :- 7Li Target :- enriched 208Pb (on Carbon backing) Beam energies :- E7Li

= 18-28 MeV

(All energies below Coulomb Barrier)

Experimental Details

T4: + 1600

T2: - 400

T1: + 400

FC

208PbT3: - 1600

7Li Beam

1 1 2 2

1 1 2 2

( , ). ( , ) ( , ). ( , )( )

( , ). ( , ) ( , ). ( , )

F F B BL L R R L L R R

B B F FL L R R L L R R

C E C E C E C ER E

C E C E C E C E

Measured Spectra

Elab (MeV)18 20 22 24 26

R(E

)

0.90

0.92

0.94

0.96

0.98

1.00

1.02

Data

7Li + 208Pb

R = 1

CDCC Calculation Details The diagonal and coupling potentials calculated using cluster folding method,

4 3( ) ( ) ( )

7 7if f t iV R r V R r V R r r

R – 7Li - target separation r - separation between clusters. Continue……

R

r

t208Pb

V

Vt

A value of DP found from a precise measurement of elastic scattering data to be, = 0.045 fm3

Loosely bound unstable nuclei (e.g. 6He, 11Li, 11Be) DP effect more important.

V. V. Parkar et al.,Phys. Rev. C (Rapid Com.), 78, 021601R (2008)

( 1, . . )8

900

B E g s n

E Enn

Polarizability parameter

For 9Be :

S. K. Pandit et al.,Phys. Rev. C

(Rapid Com.), 84, 031601R (2011)

Future prospective at ISOLDEReactions with 8,9,11Li and 7,10,11,12,14Be on similar targets to study complete reaction dynamics and compare with existing 6,7Li and 9Be data

Dipole polarizability studies for number of nuclei

GLORIA Array @

UHU, Spain

Team Members

S. Kailas, A. Chatterjee, S. Santra, A. Shrivastava, K. Mahata, K. Ramachandran, V. Jha, B. J. Roy,

S. K. Pandit, P. K. RathNuclear Physics Division, BARC, Mumbai

V. Nanal, R. G. Pillay, R. PalitDNAP, TIFR, Mumbai